The present invention relates to a system and method of controlling a steering wheel of a vehicle steering wheel assembly for simulated steering feel in a steer-by-wire system.
Steer-by-wire systems are known and continue to be improved. Steer-by-wire systems replace some mechanical linkages between the steering wheel and the vehicle road wheels with electrical wires and electronic components which send electrical signals through the wires to link the steering wheel to the road wheels of the vehicle. In order to provide a realistic feel to a steer-by-wire system, mechanisms are placed along and adjacent a steering wheel and steering shaft of the vehicle to generate resistive torque on the steering wheel. This simulates for the driver a realistic feel to the vehicle steering wheel as though the driver was driving a vehicle having a conventional mechanical steering assembly.
Although current systems and methods of providing simulated steering feel are adequate, improvements can be made thereto. When a driver of a vehicle having conventional mechanical steering gears, e.g., rack-and-pinion or recirculating ball, rotates the steering wheel to turn the vehicle in a corresponding direction, the driver experiences resistive torque especially if the steering gear assembly is without power steering. Moreover, after the turn is made, the driver typically releases torque in the direction of the turn and allows the steering gear to rotate the steering wheel back toward a center position of the vehicle. In this situation, the driver typically maintains hand position over the steering wheel, but allows the steering wheel to freely turn back toward the center position.
Manufacturers and designers of steer-by-wire systems have been challenged in producing a steer-by-wire system which adequately and efficiently simulates a torque resistance to the driver during rotation of the steering wheel and a return to center action of the steering wheel after a vehicle turn is made. Manufacturers and designers of steer-by-wire systems have also been challenged in adequately and efficiently designing a system which maintains resistance torque or return to center actions based on steering wheel inputs by the driver and external disturbances.
Thus, one aspect of the present invention is to provide a system and method of controlling a steering wheel of a vehicle steering wheel assembly for simulated steering feel in a steer-by-wire system having torque control and return to center control modes.
Another aspect of the present invention is to provide the steer-by-wire system with a control logic which switches between torque control and return to center control modes, and determines whether to maintain operating in a current control mode.
In another aspect, the present invention generally provides a system and method for simulating a feel in the steering wheel typically produced by a conventional vehicle steering assembly such as a steering wheel column and rack-and-pinion assembly. The present invention allows a vehicle operator to experience a xe2x80x9crealisticxe2x80x9d feel as the steering wheel is rotated from a center position. Further, the steering wheel driver experiences a torque resistance when the steering wheel is rotated to turn the vehicle during normal operation. As typically experienced when steering a vehicle having mechanical steering gears, e.g., rack-and-pinion and recirculating ball. The present invention further provides a realistic or simulated steering feel by returning the steering wheel back to the center position after a vehicle turn is sensed, as typically experienced when operating a vehicle with mechanical steering gears.